MicroElectroMechanical Systems (MEMS)-based microstructures, and more specifically micro-cantilever sensors, are commonly used in applications such as Atomic Force Microscopy and analyte detection, by measuring a deflection of a micro-cantilever using free space optics.
There are two common modes of operation of micro-cantilever sensors, namely a static mode and a dynamic mode of operation. In the static mode, the micro-cantilever flexes, for example, as a force is applied to it or upon the adsorption of an analyte, and an amount of movement is measured.
In the dynamic mode the micro-cantilever oscillates at or near its resonant frequency. When an analyte is adsorbed, for example, the oscillation frequency of the cantilever changes which may be measured in order to determine the presence of an analyte.
When used in Atomic Force Microscopes (AFM), an oscillating tip of the AFM is scanned at a height where it barely touches or “taps” a sample surface. An analyser monitors the sensor position and a vibrational amplitude to obtain topographical and other property information, allowing topographical information to be obtained even for fragile surfaces. One method of stimulating the micro-cantilever to oscillate is to apply an electrostatic charge to pads located on a substrate under the cantilever. Other methods of stimulating the micro-cantilever to oscillate employ piezoelectric stimulation. However these methods result in a complex sensor, and require additional equipment to generate the electrostatic or piezoelectric charge. There is therefore a need for an improved optical sensor.
The reference to any prior art in this specification is not, and should not be taken as, an acknowledgement or any form of suggestion that the prior art forms part of the common general knowledge.